The Alto has entered the 25 lakh club, where the only other car is the Maruti 800, Maruti Suzuki India (MSI) said in a statement.
"Launched in 2000, the Alto has attained the 25 lakh milestone in less than 14 years, the fastest by any brand; we are overwhelmed and humbled by its popularity," MSI Vice President (Marketing) Manohar Bhat said.
Over the years, the Alto has retained its numero uno position even amid intense competition in the small-car segment, he added.
Besides, the company has exported over 2.85 lakh units of the compact car. The Alto range now has eight variants, with prices starting at Rs 2.41 lakh.
MSI launched the Alto in September 2000. The company then introduced a 1,000-cc version of the car, the Alto K10, in August 2010.
The company said it has sold more than four lakh units of the Alto K10. MSI introduced an all-new Alto 800 in October 2012, which sported a fresh look.
"Within 124 days of its launch, the new Alto 800 attained the milestone of selling 100,000 units," the company said.
In January, MSI stopped production of the Maruti 800, the small car that was the carrier for millions of Indian middle-class families.